On calendar pages such as:

calendar/view.php?view=month

There is javascript code that updates the page live, to hide/show different calendar events.

This change isn't properly signalled to users of accessability tools and can get picked up by automated accesability audits.

I'm not sure exactly how this should be done, it's probably a fairly big task, but there's various general guides on good practice like: https://accessibility.huit.harvard.edu/provide-notification-dynamic-changes-content